The present invention relates to rotary regenerative heat exchangers generally used as air preheaters and more specifically to an improved rotor construction which maximizes the space within the rotor occupied by heat absorbent material.
A rotary regenerative heat exchanger is employed to transfer heat from one hot gas stream, such as a hot flue gas stream, to another cold gas stream, such as combustion air. The rotor contains a mass of heat absorbent material which first rotates through a passageway for the hot gas steam where heat is absorbed by the heat absorbent material. As the rotor continues to turn, the heated absorbent material enters the passageway for the cold gas stream where the heat is transferred from the absorbent material to the cold gas stream.
In a typical rotary heat exchanger, such a rotary regenerative air preheater, the cylindrical rotor is disposed on a vertical central rotor post and divided into a plurality of sector-shaped compartments by a plurality of radial partitions, referred to as diaphragms, extending from the rotor post to the outer peripheral shell of the rotor. These sector-shaped compartments are loaded with modular heat exchange baskets which contain the mass of heat absorbent material commonly formed of stacked plate-like elements.
In one type of rotary heat exchanger, support gratings extend between the diaphragms and form open supports on which the baskets are supported. The baskets are loaded into the sectors radially through the rotor shell. See for example U.S. Pat. No. 5,615,732.
For the rotation of the rotor, a pin rack assembly is mounted on the periphery of the rotor. This assembly constitutes a series of pins which are engaged by a drive gear to cause rotation. See for example U.S. Pat. Nos, 3,216,486 and 5,803,157. The presence of the pin rack assembly around the periphery of the rotor shell, usually on the cold end of the rotor, limits the access to that portion of the rotor through the rotor shell for purposes of radially loading the baskets into the rotor. It is typical that the lowermost (cold end) support grating is located above the pin rack assembly. This creates a volume at the bottom of the rotor which is void of heat absorbent material and which is essentially wasted space. This can be as great as a foot or more of rotor height thereby requiring a rotor and overall structure which are larger than necessary for the amount of heat absorbent material.